How Do Traffic Control Measures Affect Vehicle Gas Emissions

Presented by:Ryan O’Connell

Co-Authors:Kevin LuDr. Wen ChengDr. Xudong Jia

Overview

Introduction Objective Methodology Study Location Data Analysis Conclusions and Recommendations

Introduction

To ensure a safe and efficient traffic movement on the systems of roadways, a large multitude of congestion relief measures have been proposed and developed over the last century

However, most of the available methods are based solely on operational standards and rarely consider the potential impacts on emissions

Objective

To fill the gap and help researchers further understand the impacts of various traffic congestion relief measures on vehicle emissions, the main objective of this study is to explore the relationship between gas emissions and some of the most frequently used traffic control measures or devices.

Specifically, the traffic control measures investigated in the study includes stop control, yield control, pre-timed traffic signal, actuated traffic signal and signal coordination.

Methodology

Emissions analyzed: Carbon monoxide (CO)

A product of incomplete combustion and occurs when carbon in the fuel is partially oxidized. Reduces the flow of oxygen in the bloodstream and is particularly dangerous to persons with heart disease.

Nitrogen oxides (NOx) Under the high pressure and temperature conditions in an

engine, nitrogen and oxygen atoms in the air react to form various nitrogen oxides. Nitrogen oxides are precursors to the formation of ozone.

Volatile organic compounds (VOC) Are emitted both from the tailpipe and through fuel

evaporation.

Methodology

Control types analyzed: Yield

Stop

Free

Methodology

The following procedure was implemented for Synchro analysis of the study area:1. Create the traffic network in Synchro based on data

observed on Google Maps.2. Assign the different traffic control types to all

intersection approaches, e.g.: yield control, stop control, and free control.

3. Input traffic volume data (100, 500, or 1000 vehicles per hour for through lanes and 10, 50, or 100 vph, respectively, for turn lanes) at all the intersections.

4. Run the simulation for all possible combinations of traffic control measures and traffic volumes. Create reports of simulation outputs containing CO emission, NOx emission, and VOC emission.

5. Analyze the outputs in the form of charts to quantify the relationship between gas emissions and various traffic control measures.

Methodology

Fuel consumption formula (gallons): F = TT*d = k1 -TD* k2 +ST* k3

Emissions formulas (grams): CO = F*69.9 g/gal NOx = F*13.6 g/gal VOC = F*16.2 g/gal

Where k1 = 0.075283 – 0.0015892 * S+ 0.000015066 * S2

k2 = 0.7329k3 = 0.0000061411 * S2

F = fuel consumption in gallonsS = cruise speed in mphTT = vehicle miles traveledTD = total delay in hoursST = total stops in vehicles per hour

Study Location

Fresno, California

Data Analysis

Free Yield Stop0

100

200

300

400

500

600

700

Network Total with 100 vph

CONoxVOC

Traffic Control

Emiss

ion

(kg)

Emission (kg)Control Type CO Nox VOCFree 628.87 122.35 145.75Yield 5.16 1 1.2Stop 5.63 1.09 1.3

Data Analysis

Free Yield Stop0

500

1000

1500

2000

2500

3000

3500

Network Total with 500 vph

CONoxVOC

Traffic Control

Emiss

ion

(kg)

Emission (kg)Control Type CO Nox VOCFree 3131.38 609.25 725.73Yield 68.47 13.32 15.87Stop 70.79 13.77 16.41

Data Analysis

Emission (kg)Control Type CO Nox VOCFree 6272.01 1220.31 1453.6Yield 360.77 70.19 83.16Stop 365.41 71.09 84.69

Free Yield Stop0

1000

2000

3000

4000

5000

6000

7000

Network Total with 1000 vph

CONoxVOC

Traffic Control

Emiss

ion

(kg)

Conclusion

Greenhouse gas emissions from vehicles consist mostly of carbon monoxide.

Volatile organic compound emissions are slightly higher than nitrogen oxide emissions.

Emissions are proportional to assumed traffic volume. Intersections with no traffic control produce much

higher greenhouse gas emissions than those with yield control and stop control, which indicates that the fuel consumption formula may not be valid for no-control intersections.

Intersections with stop control produce slightly higher greenhouse gas emissions than those with yield control.

Recommendations

If necessary, free control would be best implemented and/or maintained at intersections with the least amount of existing traffic volume in order to minimize emissions

For intersections with higher existing traffic volumes either stop control or yield control would be appropriate

The End

Any Questions?